共查询到20条相似文献,搜索用时 468 毫秒
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淡水水体中蓝藻水华研究进展 总被引:2,自引:1,他引:1
综述目前国内大型浅水湖泊蓝藻水华成因研究现状,分析蓝藻水华形成的一般机理,重点阐明蓝藻水华治理的关键技术研究及其重要生态和环境意义。 相似文献
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AAAS Committee on Arid Lands 《Science (New York, N.Y.)》1972,175(4022):667-669
We conclude, then, that large-scale importation of irrigation water into water-deficient areas in the United States should not be undertaken simply because it is technically feasible, the water and land are available, and water deficits now or in the foreseeable future can be documented. Rather, we believe that if there is a compelling reason for large-scale water importation, it is to prevent massive social and economic disruption in an established irrigated area. 相似文献
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Water revisited 总被引:1,自引:0,他引:1
Stillinger FH 《Science (New York, N.Y.)》1980,209(4455):451-457
Liquid water consists of a macroscopically connected, random network of hydrogen bonds, with frequent strained and broken bonds, that is continually undergoing topological reformation. Anomalous properties of water arise from the competition between relatively bulky ways of connecting molecules into local patterns characterized by strong bonds and nearly tetrahedral angles and more compact arrangements characterized by more strain and bond breakage. However, these alternatives constitute virtually a continuum of architectural possibilities rather than a discrete pair of options. The singular behavior of supercooled water near -45 degrees C and the "hydrophobic" attraction between nonpolar entities are due to the same underlying phenomenon, namely, the clumping tendency of relatively strain-free convex cages or polyhedra. 相似文献
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缺水分类研究有利于制定缺水对策。在总结已有缺水分类体系的基础上,根据缺水成因,初步建立了由人为成因类、混合成因类、自然成因类三部分组成的缺水分类体系,从而提出了系统性缺水概念。系统性缺水是指在一定评价期某评价区内,人为因素决定的社会经济系统的需水时空结构与自然影响因素决定的水资源时空分布格局不协调所导致的缺水现象,属于混合成因型缺水,具有时空性、尺度性、外部性、整体性等特性,可划分为临界、早期、中期、晚期等系统性缺水阶段。 相似文献
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通过对灵江感潮河段及上游2条入境干支流水域临海市境内共5个监测断面2008—2009年溶解氧和总磷指标监测结果的有效数据收集,参照《GB3838-2002地表水环境质量标准》,对各监测断面溶解氧、总磷指标现状进行分析;同时对该流域水体污染防治和水质进一步改善提出对策。 相似文献
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[目的]定位监测高产膜下滴灌制种玉米田间土壤水分动态变化,为膜下滴灌制种玉米拔节后水分管理提供理论依据.[方法]采用时域反射仪(TDR)对膜下滴灌制种玉米田间土壤水分动态变化连续监测并分析干物质的积累情况,运用水分平衡法计算膜下滴灌制种玉米各生育时期耗水量和水分生产率.[结果]拔节期至灌浆期45d左右是玉米耗水高峰期,日平均耗水强度为6.4 mm;灌浆期日耗水强度为3.2 mm.[结论]制种玉米拔节后根区的土壤体积含水量总是维持在23.5;~31.4;(田间持水量的60;~80;). 相似文献
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水分胁迫对玉米叶片水分状况的影响 总被引:8,自引:1,他引:8
应用耐旱性不同的7个玉米品种研究了长期中度水分肋迫对玉米叶片分状况的影响,结果表明,耐旱和中度耐草品种在长期中度水分胁迫下,叶片的相对含水量和水势值的保持较高水平,总蒸腾速率和角质蒸腾速率均较低,气孔扩散阻力变化幅度大,叶细胞的质壁分离呈轻度和中度凹形,叶片具有较强的保水能力,不耐旱品种与耐旱和中度耐旱品种相比除角质蒸腾差异不明显外,其它指标均呈相反变化趋势,亦即相对含水量和水势值均较低,下降幅度 相似文献